Fastening element for connecting a support part to an add-on part

ABSTRACT

In a fastening element ( 1 ) comprised of a holding part ( 2 ) configured with a support plate ( 4 ) and expanding cheeks ( 5 ) and of a locking part ( 3 ) that is guided displaceably in said holding part ( 2 ), formed adjacent the support plate ( 4 ) are cantilevered walls ( 16 ) that are offset radially outwardly with respect to a guide wall ( 13 ), which, in order to guide the locking part ( 3 ), bears flush against the shaft portion ( 6 ). As a result, the locking part ( 3 ) can be pushed along substantially without force until it reaches inwardly protruding ramp projections ( 14 ) formed on the expanding cheeks ( 5 ), even when said expanding cheeks ( 5 ) are flexed inward, and with the advantage of a better lever ratio for spreading the expanding cheeks ( 5 ).

The invention is directed to a fastening element for connecting a support part to an add-on part according to the preamble of Claim 1.

Such a fastening element is known from DE 34 24 075 C2. The prior fastening element for connecting a support part to an add-on part is provided with a holding part, which is to be inserted into a clamping opening in the support part and which comprises a support plate and, formed on the support plate, a number of expanding cheeks that are offset radially inwardly from the support plate. Each expanding cheek has a ramp projection that protrudes radially inwardly at a distance from the support plate. The fastening element of the species in question is further equipped with an elongated locking part that can be pushed, by a shaft portion, between the expanding cheeks into the holding part through a guide opening formed in the support plate with a guide wall so as to fit flush with the locking part. The locking part moves the expanding cheeks radially outward by running up onto the ramp projection, with the result that an add-on part disposed between the support part and the support plate is connected to the support plate by the clamping action.

The object underlying the invention is to specify a fastening element of the initially cited kind, which, despite a relatively low insertion force, is distinguished by high clamping action and a high pull-out force even with relatively large tolerances in the dimensions of a clamping opening in the support part, even in the lower tolerance range.

This object is achieved according to the invention, in a fastening element of the aforesaid kind, by means of the characterizing features of Claim 1.

By virtue of the fact that a cantilevered wall that is offset radially outwardly from the guide wall is formed on each expanding cheek between the guide opening and the ramp projection, the shaft portion, after passing through the guide opening, passes in between the expanding cheeks substantially without force even if the latter are flexed inward from their idle position owing to relative underdimensioning of the throughpass opening in the support part. As a result of the [noun missing], even if the expanding cheeks are flexed—an occurrence that is not provided for per se—and, all the more so, should the holding part be disposed in a throughpass opening of a support part with substantially no interaction between these components, a foot end located in front in the insertion direction of the fastening part does not exert an effect on the expanding cheeks until it is a certain distance from the support plate, with the result that, owing to the then-favorable lever ratio, high clamping forces are induced with relatively low insertion forces.

Further useful configurations of the invention are the subject matter of the dependent claims.

The invention is described in more detail below on the basis of exemplary embodiments with reference to the figures of the drawing. Therein:

FIG. 1 is a perspective view of a first exemplary embodiment of a fastening element according to the invention, having a holding part and a locking part,

FIG. 2 is a sectional view of the exemplary embodiment according to FIG. 1 with the locking part in a pre-assembly position,

FIG. 3 is a sectional view of the exemplary embodiment according to FIG. 1 with the locking part in a final assembly position,

FIG. 4 is a perspective view of another exemplary embodiment of a fastening element according to the invention, comprising a holding part and a locking part that is provided with a latching means,

FIG. 5 is a sectional view of the exemplary embodiment according to FIG. 4 in a final assembly position of the locking part, in combination with a first embodiment of sealing elements and

FIG. 6 is a sectional view of the exemplary embodiment according to FIG. 4 in a final assembly position of the locking part, in combination with a second embodiment of sealing elements.

FIG. 1 is a perspective view of a first exemplary embodiment of fastening element 1 according to the invention, made of a hard elastic synthetic material and comprising a holding part 2 and an elongated locking part 3 that is displaceably seated in the holding part 2. The holding part 2 is provided with a flat, disk-like support plate 4, formed on one side of which are a number of expanding cheeks 5 disposed circumferentially about the locking part 3. The locking part 3 has a shaft portion 6, which is cylindrical except for a planar flattening 7 serving to secure it against rotation. The flattening 7 extends, with the formation of a stop step 10, from a head portion 8 configured with a circumferential annular groove 9 serving as a grasping aid to a foot portion 11, which is disposed oppositely from the head portion 8 and which in the arrangement according to FIG. 1 is inserted in a guide opening 12 formed in the support plate 4. The guide opening 12 is configured with a guide wall 13 that flushly surrounds the shaft portion 6, with the result that the locking part 3, guided substantially without play by the guide opening 12, can be pushed into the holding part 2 until support plate 4 butts against stop step 10 in the holding part 2.

FIG. 2 is a sectional view of the exemplary embodiment according to FIG. 1 with the locking part 3 in an extended, pre-assembly position, in which the foot portion 11 is disposed in the guide opening 12. It is apparent from FIG. 2 that the expanding cheeks 5 are configured, at a distance from the support plate 4, with radially inwardly protruding ramp projections 14, each of which has, in the longitudinal direction of the fastening element 1, a ramp wall 15 that ascends shallowly radially inward from its end proximate the support plate 4 to the end remote from the support plate 4. It can also be seen from the representation according to FIG. 2 that configured on each expanding cheek 5, between the support plate 4 and the ramp projections 14, are a cantilevered wall 16, which is offset radially outwardly from the guide wall 13, and a circumferentially extending female wall 17, which is oriented substantially perpendicular to the guide wall 13 and extends from said guide wall 13 to the cantilevered walls 16.

In the representation according to FIG. 2, the fastening element 1 is inserted in a clamping opening 19 formed in a support part 18 and through a throughpass opening 21 provided in an add-on part 20, whereupon, in this arrangement, the support plate 4 bears against the add-on part 20, and the expanding cheeks 5, by dint of having an outer wall 22 that widens radially outwardly beginning at a distance from the support plate 4 that is roughly equal to the thickness of the add-on part 20, is [sic] fixed against the support part 18 with a pre-assembly holding force that corresponds to the spring force with which the expanding cheeks 5 resist deflection.

It can further be seen from FIG. 2 that the support plate 4 has on the side facing toward the expanding cheeks 5 a radially outward, circumambient sealing lip 23, by virtue of the single-component construction of this exemplary embodiment as a hard-elastic sealing means, which protrudes in the axial direction slightly beyond a bottom wall 24 facing toward the expanding cheeks 5 and is bounded radially inwardly by a circumferential marginal groove 25 that is sunk in a circular-segment-like shape, to impart a certain deformability to the sealing lip 23.

FIG. 3 shows the exemplary embodiment explained with reference to FIGS. 1 and 2 with the locking part 3 in a final assembly position in which it is pushed into the holding part 2. It is apparent from FIG. 3 that space exists in the radial direction between the head portion 8 of the locking part 3 and each cantilevered wall 16, with the result that only after a certain insertion movement of, for example, approximately one-third the length of the expanding cheeks 5 has been executed in the axial direction substantially without force, even when the expanding cheeks 5 are biased radially inward, for example due to a clamping opening 19 that is dimensioned in the lower tolerance range, does it transpire that the foot portion 11 comes into contact with the ramp walls 15 of the ramp projection 14 and the expanding cheeks 5 flare, thus clamping the holding part 2 in the clamping opening 19 of the support part 18. By virtue of the clamping action that occurs after the expanding cheeks 5 flare out in the radial direction, the fastening element 1 is stably anchored in the support part 18 with a high pull-out force, the sealing lip 23 resting with a slight bias flush against the add-on part 20 and thereby sealing the clamping opening 19 and the throughpass opening 21.

In addition, because the foot portion 11 acts on the ramp projection 14 at a relatively large distance from the support plate 4, a favorable lever ratio for spreading the expanding cheeks 5 is obtained, and is even preserved when the expanding cheeks 5 are flexed radially inwardly and are over-biased due to a too-small diameter of the clamping opening 19 compared to the nominal diameter.

To release the fastening element from engagement with the support part 18, the locking part 3 can be grasped, for example with two fingers or by means of a gripping tool, preferably in the region of the annular groove 9, and moved back out of the final assembly position shown in FIG. 3 into the pre-assembly position shown in FIG. 2, so that the fastening element 1 can again be removed from the support part 18.

FIG. 4 is a perspective view of another exemplary embodiment of a fastening element 1 according to the invention, it being noted that like elements in FIGS. 1 to 3 and in FIG. 4 are provided with the same reference numerals and will not be described more closely below. It can be seen from FIG. 3 that in the second exemplary embodiment, formed as a latching means on the shaft portion 6 of the locking part 3 is an elastic latching tongue 26, which projects radially beyond shaft portion 6 and extends in the direction of head portion 8, and which is able to dip toward the shaft portion 6 into a clearance 27.

In the second exemplary embodiment according to FIG. 4, configured in the head portion 8 of the locking part 3 is a circumambient elastic head seal 28 made of soft elastic media, also projecting radially outwardly beyond the shaft portion 6. Finally, in the second exemplary embodiment the head portion 8 comprises, on the side facing away from the shaft portion 6, a head plate 29, which also projects radially outwardly beyond the shaft portion 6.

FIG. 5 shows the second exemplary embodiment according to FIG. 4 after the locking part 3 has been shifted from the pre-assembly position shown in FIG. 4 into a final assembly position, in which, by suitable adaptation of the distance between the free end of the latching tongue 26 and the side of the head plate 29 facing toward the latching tongue 26, the latching tongue 26 rearwardly engages the female wall 17 and thereby locks the locking part 3 in the holding part 2 with a high pull-out force, until a [words missing] the fastening element 1. In the final assembly position, the head seal 28 is compressed by contact with the guide wall 13 of the guide opening 12.

It can also be seen from FIG. 5 that in a first embodiment of the sealing means, formed onto a circumambient edge web 30 configured radially outwardly of the head plate 29 is an elastic collar lip 31 made of a soft component, which approximately matches the radial extent of the side of the support plate 4 facing toward the expanding cheeks 5. The collar lip 31 thus has a relatively large contact area with the add-on part 20, resulting in good sealing action.

FIG. 6 shows the second exemplary embodiment according to FIG. 4 and FIG. 5 with another embodiment of sealing means. In the embodiment according to FIG. 6, the sealing means comprise, in the radially outer edge region of the support plate 4, a bridging lip 32 made of a soft component, which is joined flush to a smooth outer edge wall of the support plate 4, and which brings about satisfactory sealing action with less material expenditure than in the case of the embodiment of FIG. 5. 

1-6. (canceled)
 7. A fastening element for connecting a support part to an add-on part, comprising: a holding part including a support plate having a guide opening with a guide wall, and a plurality of expanding cheeks formed onto said support plate and offset radially inwardly from said support plate, each expanding cheek including, at a distance spaced from said support plate, a radially inwardly protruding ramp projection and an outer wall that widens radially outwardly, each said expanding cheek further including a cantilevered wall adjacent said support plate and disposed between said guide opening and said ramp projection, each said cantilevered wall offset radially outwardly from said guide wall of said guide opening; and an elongated locking part insertable through said guide opening in said support plate and between said expanding cheeks, said locking part including a shaft portion and a guide wall having a flush fit within said guide opening, said locking part engageable with said expanding cheeks to move said expanding cheeks radially outwardly by running up onto said ramp projections of said expanding cheeks.
 8. The fastening element of claim 7, wherein each said cantilevered wall extends from said support plate to said ramp projections.
 9. The fastening element of claim 7, wherein said locking part includes a head portion that faces away from said holding part, and an annular groove disposed between said shaft portion and said head portion.
 10. The fastening element of claim 7, wherein said shaft portion includes an elastic head seal projecting radially beyond said shaft portion, said head seal bearing against said guide wall in a pushed-in position of said locking part.
 11. The fastening element of claim 7, wherein each said expanding cheek further includes a female wall disposed between said support plate and said cantilevered wall, said female wall one of perpendicular and steeply oblique to said cantilevered wall, and said shaft portion includes an elastic latch, said elastic latch rearwardly engageable with said female wall in a final assembly position of said locking part.
 12. The fastening element of claim 11, wherein said support plate includes at least one elastic seal bearing against an add-on part when said female wall is rearwardly engaged by said elastic latch in said final assembly position. 